This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this study is to test whether Nestorone gel in combination with Testosterone gel will be better in suppressing sperm production than testosterone (T) gel alone. This study is being done with a long-term goal to develop new male contraceptives that are safe, effective, self delivered, easy to use, reversible, and affordable. Currently, contraception options available to men are limited to condoms and vasectomy. Testosterone gel being used in this study has been approved by the FDA for the use in hypogonadal men (with low blood testosterone levels) and is available under names AndroGel[unreadable][unreadable] and Testogel[unreadable][unreadable]. Nestorone gel is a new derivative of progestin (female hormone). The study will take 10 to 11 1/2 months to complete. Potential subjects will not be allowed to have used hormonal therapy in the 6 months preceding study screening. Potential subjects will be required to use an approved and effective method of contraception, such as condom, for the duration of the study. Eligibility will be determined during screening visits based on medical history, physical examination including digital rectal exam, laboratory tests done on blood (including hormones) and urine, and sperm analysis. Subjects will collect sperm samples by masturbation in a private room at the doctor s office. Subjects will be required to abstain from ejaculation for 2-5 days prior to study visits when sperm samples are to be collected.